main(List<String> args) {
  // 定义字符串
  var str1 = 'abc';
  var str2 = "abc";
  var str3 = """
    abc
    cde
    fgh
  """;

  // 字符串和表达式进行拼接
  var name = "lyc";
  var age = 19;
  var height = 1.75;

  var message1 = 'name: ${name}, age: ${age}, height: ${height}';
  var message2 = "name is $name, type: ${name.runtimeType}";

  print(message2);
}
